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Full text of "Text Book Of Mechanical Engineering"

Steam Cylinder in Loam.                          21

way. A few sprigs or brads in the flanges N serve to fasten the
latter to the pattern.

The mould for a Large Steam Cylinder is usually made
entirely in loam, and this operation we will now examine.

Fig. 27 represents the casting in longitudinal section, elevation,
and in plan. The valve box is made separately, as is sometimes
done with these large cylinders, but in any case, no further
explanation is needed be^nd that previously given, as a pattern
would be made for it. The body of the cylinder would be swept
out entirely by template boards, but special projections, such as
steam ports and exhaust flange, would require core boxes and
patterns.

An iron plate A, Fig 27^, is laid on the foundry floor to
support the structure, and a centre B is sunk beneath the ground-
line, an upright spindle c being taken of sufficient length, and
supported at the top by means of an arm D standing out either
from the wall or from a crane pillar; all is now ready to
begin.

A base of loam is swept out by the board E, shown in dotted
lines, and representing the bottom of the cylinder flange ; this is
dried and blackwashed, a flat ring d being then laid as a foundation
for the core structure.

Taking board E away, another (e) is used to strike out the
lower cylinder flange f, which is necessary as a support to help
plate d.

The loam/being dried and blackwashed, the external core of
the cylinder is next formed, because it is necessary to remove it
for the formation of the internal core, and the latter, being in one
piece and cumbrous, is made separately. The board F is now
used to strike the outer form, the central projection being for the
exhaust port, and an opening must be allowed at G, the full length
of the cylinder (see Fig. 29) for the reception of the port cores on
one side, and which may be traced out by a template board, while
a similar opening g, of the depth K j, must be left on the opposite
side for the exhaust flange core. It will be noticed that this outer
mould requires, for building, the aid of annular plates at H j K L M,
for the support of different pieces of the structure. These plates
do not go entirely round, being prevented by the ports at G, and